Noisy Alternator

danbhoy1888

danbhoy1888

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19 Jun 2006
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Ayrshire Scotland
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When starting my engine from cold there is a sqealing noise like a fan belt slipping,I checked serpantine belts and they are o/k.I have been told by the dealer where I got the boat that this is normal and it is the alternator. I have noticed when starting from cold the battery condition gauge reads below 12 volts and the squeal stops when it reaches 14. I have tried 3 different charged batteries and it is just the same. I have tested the alternator
and it is charging ok. My boat is a Bayliner 2255 with 4.3L Mercruiser. Is the noise just the alternator starting to charge or is there a problem ?
 
A noise is never good, might be minor, but isn't right. Cann you take off the alternator belt just to try it to isolate the cause of the noise?

Have you tried putting on your spare belt to see if that helps?

If it is the actual alternator (as opposed to the belt) then prob just the bearings, most can be repalced at reasonable cost.

Ants
 
danbhoy1888 said:
When starting my engine from cold there is a sqealing noise like a fan belt slipping,I checked serpantine belts and they are o/k.I have been told by the dealer where I got the boat that this is normal and it is the alternator. I have noticed when starting from cold the battery condition gauge reads below 12 volts and the squeal stops when it reaches 14. I have tried 3 different charged batteries and it is just the same. I have tested the alternator
and it is charging ok. My boat is a Bayliner 2255 with 4.3L Mercruiser. Is the noise just the alternator starting to charge or is there a problem ?
Click to expand...
Its the belt slipping under load, check the tension, be aware that when v belts wear they wear on the side (which is where the drive is taken from) then when you tighten them they bottom out and lose the drive/friction on the sides so worsening the situation. This applies to multiv belts as well. Also do you have a power steering pump on yours, if so, that could be the culprit as well.
Same situation
Stu
 
Alternator drives

There are several reasons why a belt will slip whilst trying to transmit drive. The first and most obvious is belt condition and tension which is fairly self explanatory. If the drive is still making a noise then consider that there may be wear in the pulleys. before starting up and , of course making sure that no one can start up the engine, put your little finger up inside the vees of the pulleys. If you can feel more than about 2mm on either side of the vees then you may need new pulleys.
Is everything on this setup original? Do the the parts look the same as in the parts book?
Another one to look out for is that the pulleys are not lining up with each other. This only usually happens when some one has tried to upgrade the original alternator for something bigger, although I have had situations where brackets been bent whilst engine have been lifted into position. Stretch a peice of twine over the front face of the crank pulley to give yourself an idea of where the alternator should be.
 
danbhoy1888 said:
Yes I have a power steering pump as well, I am in the process of ordering new drive belts from Tricket Marine as I dont know if anyone near me in Ayrshire stocks them.
Click to expand...

Copy the number from your belt and take it to your nearest motor factor or Fenners and they will match it, and much cheaper than getting it from your marine supplier - and quicker too. There is bound to be a belt supplier in Ayr or nearby. :)
 
A squeeling on start up which goes away after a short time is almost certainly a belt slipping. It's caused by the initial load on the alternator. Next time you start up spray some water on the suspected belt at one of the pulleys. I bet the squeeling will stop or at least change tone. This will confirm a slipping belt. As for a new belt take the old one into a motor factors and they will match a new one for you.
 
Just an update still waiting for new belts arriving, but have since found that it is my alternator belt slipping I managed to get a wee bit more tension on it and the noise has stopped, the alternator belt has a bit of wear and the underside is hard,I will replace it when the new belt arrives.I am sure they are the correct belts because the numbers check out however there are a lot of different belts fitted to the 4.3l Mercruiser as I have found out on my searches and nobody in Scotland stocks any of them.Thanks again to everyone I will update as soon as I fit my new belts.
 
danbhoy1888 said:
New belts finally arrived on Friday £ 41.00 fitted Today no noise on start up,old alternator belt a bit worn compared to new one. Problem solved, thanks to everyone for advice.
Click to expand...
Dont forget to retighten after a couple of hours when they have bedded in
Stu
 
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